The invention encompasses all screws designed to provide for attachment or assembly by virtue of being installed in a threaded hole in a complementary part. This is true, for example, of screws designed to work in conjunction with a nut, or of those intended to fasten at least two pieces together by virtue of being screwed into the threads of a threaded hole provided within at least one of these pieces.
One disadvantage of these conventional screws lies in the fact that the installation and removal thereof may entail relatively long, laborious operations.
In fact, the installation of a screw requires the following operations, performed in this order: 1) engagement of the screw threads into the threads of the complementary piece; 2) rotation of the screw until the screw head rests on one of the pieces; 3) tightening of the screw into the complementary piece by effecting a certain number of turns or partial turns once the screw head rests on the piece.
Removal of the screw requires the following operations: 1) loosening; 2) rotation of the screw to disengage the threads from the threading in the complementary piece; 3) removal of the screw from the complementary piece.
In fact, the rotation step (the second step involved in the installation or removal summarized above) are the most lengthy. This may be bothersome when the screws are, for example, designed to fasten individualized parts on a machine tool. It is desirable in this case that the stoppage of the machine, as required in order to replace these parts, be as short as possible, so as to reduce operating costs, while not decreasing excessively the production capacity thereof.
The present state of the art includes devices which allow fastening or disassembly in a short time. However, these known devices normally provide inferior fastening quality: they exhibit either pronounced sensitivity to vibrations or inferior mechanical strength.
Thus, for example, quarter-turn or bayonet-type locking devices are known, in which a lug borne by an attachment rod is engaged and locked, following a slight degree of rotation, in a slot-and-cam mechanism which locks another part in place.
These devices exhibit a certain level of elasticity, which makes them unsuitable for attaching pieces subjected to vibrations, for example.
Thus, the invention concerns a device which can be installed and removed rapidly, but which does not possess the disadvantages of conventional devices.